1. Field of the Invention
The present invention relates to the art of rendering and color matching with an imaging device such as a printing device.
2. Description of the Related Art
Conventionally, at the time of outputting color specified in rendering commands in a PDL (Page Description Language) document to a monitor or printer (output device), the PDL document is subjected to gamut mapping/conversion. This gamut mapping/conversion is performed using a profile (ICC profile or the like) of the output device, to perform mapping/conversion of the PDL document into the gamut of the output device. This method is described in Japanese Patent Laid-Open No. 7-107312, for example.
Also, Japanese Patent Laid-Open No. 8-235346 describes converting objects having different attributes (color space, etc.) into respective optimal image data structures, and switching the color matching processing to be applied to the image data structure in real-time.
There are cases wherein opacity (alpha value) is included in PDL document rendering commands as a color specification. Alpha blending is necessary in the event that an image according to rendering commands having opacity and an image according to other rendering commands overlap. In such instances, rendering results differ depending on whether mapping to the gamut of the output device (e.g., a printer) before performing the alpha blending for the rendering commands, or performing alpha blending after mapping to the gamut of the output device. However, there is no single factor which determines which timing for gamut mapping would be better. Rendering results are affected by the colors and alpha values specified in the rendering commands, the output device, profiles used at the time of gamut mapping, rendering intent, and so forth.
Also, in the event that a paint command in the PDL document includes gradient, gradient rendering is necessary. In this case as well, rendering results differ depending on whether mapping to the gamut of the device is performed before performing gradient rendering, or performing gradient rendering is performed before mapping to the gamut of the device. As can be seen here, whether to perform color matching before or after certain types of rendering such as alpha blending and gradient needs further consideration.